Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus triangularis  (Lagerheim) Teiling

Widespread but infrequent in circumneutral waters such as loch-margins and pools

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland
Teiling, E. (1967) The desmid genus Staurodesmus. A taxonomic study